OSTRACOD-BASED RECONSTRUCTION OF BOTTOM WATER CONDITIONS IN THE INNER SEA OF THE MALDIVES DURING THE PLEISTOCENE (IODP SITE U1467, NORTHERN INDIAN OCEAN)

The Maldives carbonate archipelago has been shaped by sea level change, ocean currents, and the onset and intensification of the South Asian Monsoon (SAM). The SAM is an intense climatic phenomenon that provides ample precipitation to southern Asia and is linked to a seasonal reversing wind pattern that controls the modern ocean circulation and productivity in the north and central Indian Ocean, as well as the development of the oxygen minimum zone (OMZ) in the water column. International Ocean Discovery Program (IODP) Expedition 359 drilled eight sites (U1465-U1472) in the carbonate edifice across the Maldives to reconstruct changes in sea level and ocean circulation, as well as monsoon evolution in this mostly unread archive of the Indian Ocean.

Site U1467 was cored to 630 m below the sea floor in the Inner Sea at a water depth of 487 m. Because of its location in the center of The Maldives, the Inner Sea is a natural sediment trap. Cores recovered at this site yielded a continuous Miocene to Holocene sedimentary sequence with abundant and well-preserved calcareous microfossils, including ostracods. The focus of this study is to reconstruct glacial/interglacial changes in bottom water ventilation and circulation, and changes in the OMZ related to Monsoon dynamics throughout the Pleistocene by analyzing the deep-sea ostracod record at Site U1467. Ostracods will be compared and discussed within a multiproxy dataset including benthic foraminifera, alkenones, stable isotopes, sediment physical properties, and X-ray fluorescence spectrometry. Results show that ostracod variability reflects Pleistocene changes in sea-level, bottom water ventilation, and monsoon intensification in the northern Indian Ocean.